Systems and methods for reducing a relatively high power, approximately constant envelope interference signal that spectrally overlaps a relatively low power desired signal

Abstract

Systems and methods are provided for processing time-domain samples of a digitized signal in rectangular coordinates. The digitized signal can include a low power desired signal and a high power, approximately constant envelope interference signal that spectrally overlaps the desired signal. A rectangular to polar converter can obtain magnitude and phase of each time-domain sample in polar coordinates. An interference estimator can estimate a magnitude of the interference signal based on magnitudes of a predetermined number of time-domain samples in polar coordinates. A subtractor can obtain a difference magnitude for each time-domain sample in polar coordinates based on the magnitude of that sample and the estimated magnitude of the interference signal in polar coordinates. A polar to rectangular converter can obtain time-domain samples in rectangular coordinates of the desired signal with reduced power of the interference signal based on the difference magnitude and phase of time-domain samples in polar coordinates.

Description

FIELD OF THE INVENTION[0001]This application relates to systems and methods for reducing an interference signal that spectrally overlaps with a desired signal.BACKGROUND OF THE INVENTION[0002]Strong interference has become a common problem as the radio spectrum has become more crowded. Constant envelope, or approximately constant envelope signals are popular because such waveforms are compatible with non-linear amplifiers which can be more energy efficient than linear amplifiers. Examples of constant envelope signals include: frequency modulation, frequency shift keying, minimum shift keying, Gaussian minimum shift keying, multi-h continuous phase frequency modulation, linear FM, continuous wave, and many frequency hopping signals. Any of these types of constant envelope signals can cause interference with other, desired signals, particularly where the desired signal and the constant envelope signal spectrally overlap with one another.[0003]Because constant envelope interference is ...

AI Technical Summary

Benefits of technology

The present invention provides a way to reduce interference from a high power signal that has the same frequency as a low power desired signal. The system can suppress the interference in a simple way, using fewer steps and resources, and can be applied to a wide range of signals without needing to customize it for each type.

Problems solved by technology

Strong interference has become a common problem as the radio spectrum has become more crowded.

Any of these types of constant envelope signals can cause interference with other, desired signals, particularly where the desired signal and the constant envelope signal spectrally overlap with one another.

This adaptive approach requires time to converge, and even then a narrow band signal buried beneath a wide-band strong interference signal might not be recovered because the steady state transfer function is frequency selective.

However, such an approach can be computationally complex.

Unknown signals, such as proprietary waveforms, might render successive interference cancellation or joint demodulators impractical.

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